The Effect of Human Occupancy on Indoor Air Quality through Real-Time Measurements of Key Pollutants

Abstract

The primarily emitted compounds by human presence, e.g., skin and volatile organic compounds (VOCs) in breath, can react with typical indoor air oxidants, ozone (O 3 ), and hydroxyl radicals (OH), leading to secondary organic compounds. Nevertheless, our understanding about the formation processes of the compounds through reactions of indoor air oxidants with primary emitted pollutants is still incomplete. In this study we performed real-time measurements of nitrous acid (HONO), nitrogen oxides (NO x = NO + NO 2 ), O 3 , and VOCs to investigate the contribution of human presence and human activity, e.g., mopping the floor, to secondary organic compounds. During human occupancy a significant increase was observed of 1-butene, isoprene, and d-limonene exhaled by the four adults in the room and an increase of methyl vinyl ketone/methacrolein, methylglyoxal, and 3-methylfuran, formed as secondary compounds through reactions of OH radicals with isoprene. Intriguingly, the level of some compounds (e.g., m/z 126, 6-methyl-5-hepten-2-one, m/z 152, dihydrocarvone, and m/z 194, geranyl acetone) formed through reactions of O 3 with the primary compounds was higher in the presence of four adults than during the period of mopping the floor with commercial detergent. These results indicate that human presence can additionally degrade the indoor air quality.

Human skin oil: a major ozone reactant indoors

“…Additional results and implications from this study are presented in Section 4.2. Deng et al 69 made real-time measurements of naturally occurring nitrous acid, nitrogen oxides, ozone, and organics in an apartment room in Guangzhou, China. In this study, researchers used scripted activities (e.g., opening/closing windows, and mopping) and deliberately varied the number of occupants in the room.…”

Ozone Chemistry on Greasy Glass Surfaces Affects the Levels of Volatile Organic Compounds in Indoor Environments

“…It has to be noted that these levels of secondary VOCs were produced by a relatively high O 3 mixing ratio of 50 ppb. Nevertheless, in recent measurements in the same apartment in Guangzhou during 2 days of the campaign, we detected indoor O 3 levels of 40 and 50 ppb when the outdoor O 3 was exceeding 80 ppb. Recent studies reported O 3 mixing ratios of more than 100 ppb in Guangdong-Hong Kong urban area. , Hundreds of O 3 pollution days exceeding O 3 levels over 100 ppb were also observed in Shanghai metropolitan area .…”

“…We also detected 6-MHO which can be formed by ozonolysis of terpenoids such as geraniol, linalool, or citral, , and the subsequent reaction between O 3 and 6-MHO leads to the formation of 4-OPA (Table S1). ,− Indeed, it has been shown that terpenoids released from cleaning detergents can be deposited on the glass surfaces and react toward O 3 . ,, There is a solid evidence that in the presence of occupants, the most prominent source of 6-MHO would be the reaction of O 3 with human skin lipids (squalene). ,,,,,,,,− Combining the evidence of a substantial amount of decanal and 6-MHO, an implication could be that in addition to the cooking oils, skin oil might be transferred to the glass plate by deposition of vapor or particles containing skin flakes . Namely, Liu et al highlighted the importance and possible mechanism of “off-body skin oil”.…”

“…31,82−84 Indeed, it has been shown that terpenoids released from cleaning detergents can be deposited on the glass surfaces and react toward O 3 . 42,80,85 There is a solid evidence that in the presence of occupants, the most prominent source of 6-MHO would be the reaction of O 3 with human skin lipids (squalene). 15,23,27,29,30,32,52,72,85−87 Combining the evidence of a substantial amount of decanal and 6-MHO, an implication could be that in addition to the cooking oils, skin oil might be transferred to the glass plate by deposition of vapor or particles containing skin flakes.…”

Efficient Catalytic Elimination of Toxic Volatile Organic Compounds via Advanced Oxidation Process Wet Scrubbing with Bifunctional Cobalt Sulfide/Activated Carbon Catalysts

“…Volatile organic compounds (VOCs), the primary precursors of ozone and haze formation, would cause harmful effects to human health and ecosystems due to their toxic, malodorous, mutagenic, and carcinogenic properties. − Among them, aromatic VOCs such as styrene, toluene, and chlorobenzene are a growing environmental concern due to their increasing emissions in the plastics, printing, and electronics industries. According to the Clean Air Act Amendments amended by the Environmental Protection Agency of the United States, these aromatic VOCs are very toxic to human beings and have been listed as potential carcinogens .…”